1. Field of the Invention
The present invention relates to a multi-speaker sound imaging system, and more particularly, to an audio system that generates multi-channel imaging from two-channel recording, for improved user listening.
2. Description of the Related Art
Typically, musical systems for recording, storing and reproduction are made utilizing a two-channel system. The two-channel recording system basically works by mixing multiple instrument, voice, effects, and other sound signals, all of which produce as a resultant two signals or channels, which in turn are recorded in different media as CDs, tapes, etc. Additionally, two-channel amplifiers drive loudspeakers to reproduce these signals for listening.
The mixing process during two-channel recording is very important because the relative spatial positioning of all music components such as instruments, vocals, and all other sound signals, will be defined in this process. One objective of stereo reproduction is to permit the listener to perceive the original spatial distribution of the different sounds involved in the recording. Present musical systems work optimally only if the listener is in perfect geometrical and acoustical symmetry with respect to the two reproducing channels. The use of headphones permits a good approach to optimal stereo listening.
The fact that stereo listening depends on the position of the listener with respect to the two reproducing channels, has hindered optimal stereo listening. This is especially true with sounds that are common to both channels, which in the majority of recordings, includes the vocalist or singer.
In sub-optimal conditions, existing stereo systems do not give the listener the sensation of being in front of a vocalist or singer, but a sensation that the voice is distributed in space, and not located in a fixed position. Under this condition, the listener looses one of the most important sensations derived from listening to recordings, to be in the presence or in front of the vocalist or singer.
Some designs for improving the image for stereo systems have been done in the past. None of them, however, include a multi-channel of four or more even number of channels as a reproduction technique for stereo signals.
The multi-channel imaging is done by an electronic circuit that generates four or more even number of separate channel output signals, derived from the processing of two-channel recordings. The resulting signals are fed to amplifiers, which drive speakers located at defined positions. This permits, in the listening area, the listeners to perceive an audible sensation of having the singer in front of them and allowing the remainder of the music signals to be distributed according to the original recording thus giving the spatial sensation.
Practical experimentation with different speaker arrays has determined the positions in which the objective of frontal hearing is reached. Results were found to be the geometric places where the listener is symmetrical to any two speakers of an array.
Applicant believes that an approach corresponds to U.S. Pat. No. 5,610,986 issued to Miles for Linear-Matrix Audio-Imaging System and Image Analyzer. Miles teaches an audio-imaging system including at least first and second input channels for receiving first and second channel audio input signals and at least first, second and third output signals which are produced as a combination of the first and second channel audio input signals and a parameter, which is applied to the first, second and third output signals in order to compensate for composition mixing of the program source. The parameter can be varied by the user or determined by a sound image analyzer circuit.
Other patents describing the closest subject matter provide for a number of more or less complicated features that fail to solve the problem in an efficient and economical way. No patents suggest the novel features of the present invention.
The present invention utilizes, in its basic form, a single row speaker array with an even number of four or more speakers, all of these driven by amplifiers, permitting a lateral distribution similar to that of the original stereo recording. For central positioned signals, that is, for signals from the singer and instruments located at the center of a recording, the present sound imaging system simultaneously reproduces them into each of its output channels. The reproduction of these signals will give, in the listening area, a sound distribution that will cause the listeners a sensation of having the singer in front of them, while perceiving the spatial distribution of the recording.
With the present invention, instead of having two speakers in front of the listeners there can be four, six, eight or more, evenly arranged, preferably in a linear form, when using a single row speaker array. In order to obtain the maximum benefits of the present invention, the speakers, as well as the amplifiers, should have complementing characteristics and be of the same types.
The sound imaging system can be used in homes, cars, theaters, cinemas, and other locations where there is a need of stereo recordings listening. An additional benefit to utilizing multiple speakers in wide or spacious places is that the sound will be better distributed in the area, with lower decibel level per speaker, making it safer for the hearing of individual listeners.
Additionally, the sound imaging system is compatible with all stereo recordings and stereo systems.
More specifically, the instant invention is a sound imaging system, which by processing left and right stereo channel audio signals of a conventional two channel stereo system, distributes signals to a speaker array of a number of speakers determined by a listening area, in which listeners located in different places within the listening area, can have an audible perception of an equivalent distribution to that of the conventional two channel stereo system. Additionally, the listeners have an audible central perception of the centred program material equivalent to that obtained from the conventional two channel stereo system when the listeners are located in a median plane of the conventional two channel stereo system speakers.
The instant invention comprises first and second input channels for receiving the left and right stereo channel audio signals, four or more even number of output channels delivering four or more even number of audio output signals respectively as a result of processing the left and right stereo channel audio signals. The four or more even number of audio output signals are a function of the left and right stereo channel audio signals, and an adjustable parameter.
The first and second input channels are configured to receive the left and right stereo channel audio signals from the conventional two channel stereo system. The four or more even number of output channels are configured to be connected to a same number of audio amplifiers in order to drive four or more even number of speakers set as the speaker array.
A method for determining the adjustable parameter is presented by making equal a first summing localization of a first audio image produced by two sound sources to a second summing localization of a second audio image produced by four or more sound sources, where for the two sound sources:       D    ST    =                              S          1          xe2x80x2                ·                  D          1          xe2x80x2                    +                        S          2          xe2x80x2                ·                  D          2          xe2x80x2                                    S        1        xe2x80x2            +              S        2        xe2x80x2            
in which Sxe2x80x21 is a first signal amplitude at a first distance Dxe2x80x21 from an origin, Sxe2x80x22 is a second signal amplitude at a second distance Dxe2x80x22 from the origin, the first summing localization of the first audio image is located at a distance DST from the origin, wherein Sxe2x80x21 and Sxe2x80x22 are signals of same frequency and phase, but different amplitude. For the four or more sound sources:       D    MSI2N    =                    ∑                  j          =          1                          2          ⁢          n                    ⁢              xe2x80x83            ⁢              (                              D            j                    ·                      S            j                          )                            ∑                  j          =          1                          2          ⁢          n                    ⁢              S        j            
in which Sj is the amplitude of the j source, j is any of 2n sources, 2n is the number of the four or more sound sources, Dj is the distance between the four or more sound sources and the origin, the second summing localization of the second audio image is located at a distance DMSI2N from the origin, wherein Sj are signals of same frequency and phase, but different amplitude.
The four or more even number of audio output signals that are amplified by the audio amplifiers, which in turn drive the speaker array, have a first output channel with a first signal of the type: S1=(L+C)+Kxc2x7(Lxe2x88x92R), a last output channel with a last signal of the type: S2n=(R+C)+Kxc2x7(Rxe2x88x92L), producing said four or more even number of audio output signals of the type: Sj=C+Lxc2x7Mxe2x88x92Rxc2x7(Mxe2x88x921) as a result of multiple signal divisions between the first signal and the last signal, where 2n is a number of the four or more even number of audio output channels, j is any of 2n output channels with an integer value from 1 to 2n, (L+C) is the left stereo channel audio signal, (R+C) is the right stereo channel audio signal, C is a central program audio signal of the left and right stereo channel audio signals, (Rxe2x88x92L) is a result of the difference of the left stereo channel audio signal from the right stereo channel audio signal, (Lxe2x88x92R) is an inverted (Rxe2x88x92L) signal,       M    =                  1                              2            ⁢            n                    -          1                    ⁡              [                              K            ⁢                          {                              1                +                                  2                  ⁢                                      (                                          n                      -                      j                                        )                                                              }                                +                      2            ⁢            n                    -          j                ]              ,
and K is the adjustable parameter.
The speaker array comprised by the four or more even number of speakers, is arranged in a horizontal pattern, with equal distances between contiguous speakers, and positioned in such a way that the conventional two channel stereo system speakers are replaced by the speaker array of the four or more even number of speakers.
The speaker array is located in such a position that, at a first predetermined distance in between a first speaker of the four or more even number of speakers and one-third of a total width of the speaker array taken from the left, is a left speaker equivalent position of the conventional two channel stereo system and that, at a second predetermined distance in between a most right speaker and one-third of the total width of the speaker array taken from the right, is a right speaker equivalent position of the conventional two channel stereo system. The speaker array is symmetrically positioned to the conventional two channel stereo system speakers equivalent locations.
A 2n even number of four or more speakers comprising the speaker array and a positioning of the speaker array with respect to the conventional two channel stereo system speakers within the first and second predetermined distances for the listening area, determine a value of the adjustable parameter, when making the second summing localization of the second audio image positioning generated by the speaker array equal to the first summing localization of the first audio image generated by the conventional two channel stereo system speakers. The adjustable parameter being adjustable by a user.
A listening area width will determine a selection of the 2n even number of four or more speakers.
The instant invention has a first adjustment means for the user, for adjusting a number of the four or more even number of output channels by means of electrical switch selectors. Additionally, the instant invention includes a second adjustment means for the user, for adjusting the adjustable parameter by means of a potentiometer.
The adjustable parameter is adjustable within a range of 0 and 1, and a value for the adjustable parameter is displayed.
The four or more even number of output channels are connected respectively with the amplifiers driving the 2n even number of four or more speakers. Each positioned in the speaker array, wherein the 2n even number of four or more speakers originate (4nxe2x88x923) listener position lines within the listening area which are perpendicular to the speaker array.
The listening area of the sound imaging system has a width extension located in between a center point of two most left speakers and a center point of two most right speakers of the speaker array, which is a single row speaker array in the preferred embodiment.
A multiple number of the speaker arrays installed horizontally and connected in parallel by columns, are used when the extension of the depth of the listening area requirements so demand.
It is therefore a main objective of the present invention to provide a new reproduction technique for stereo music that basically consists in reproducing signals that are common to stereo channels, especially singers and vocalists, in such a way that they can be perceived as centered by different listeners, in a wider space than that available from a conventional stereo system, while maintaining the spatial distribution of the recording.
It is another object of this invention to provide such a device that is inexpensive to manufacture and maintain while retaining its effectiveness.
Further objects of the invention will be brought out in the following part of the specification, wherein detailed description is for the purpose of fully disclosing the invention without placing limitations thereon.